Facebook登录按钮未分段显示

Question

我在我的项目中做了Facebook登录。它在活动中效果很好。我只是尝试添加片段。因为，登录后我希望用户可以logout和Facebook button一起使用此片段中的内容。但是Facebook登录button不会出现在模拟器中。怎么解决呢？

AccountFragment.java

import android.content.Context;
import android.content.Intent;

import android.support.annotation.NonNull;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;

import android.widget.Toast;

import com.bumptech.glide.Glide;
import com.bumptech.glide.request.RequestOptions;
import com.facebook.AccessToken;
import com.facebook.AccessTokenTracker;
import com.facebook.CallbackManager;
import com.facebook.FacebookCallback;
import com.facebook.FacebookException;
import com.facebook.GraphRequest;
import com.facebook.GraphResponse;
import com.facebook.login.LoginResult;
import com.facebook.login.widget.LoginButton;

import org.json.JSONException;
import org.json.JSONObject;

import java.util.Arrays;

public class AccountFragment extends Fragment {

    private Button buttonLogout, buttonAccount;
    // Facebook login için
    LoginButton buttonFbLogin;
    private CallbackManager callbackManager;

    public AccountFragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {



            buttonFbLogin = view.findViewById(R.id.fb_button);    //Facebook button
            buttonLogout=view.findViewById(R.id.button_acc_Profile_Logout);  // uygulamanın Logout butonu
            callbackManager = CallbackManager.Factory.create();    // FB için
            buttonFbLogin.setReadPermissions(Arrays.asList("email","public_profile"));  //FB için
            buttonFbLogin.setFragment(this);

            checkFacebookLoginStatus();
            //facebook buton tıklandığı zaman yapılacak login için
            buttonFbLogin.registerCallback(callbackManager, new FacebookCallback<LoginResult>() {

                @Override
                public void onSuccess(LoginResult loginResult) {
                    Intent intent = new Intent(getContext(), MainActivity.class);
                    startActivity(intent);
                }

                @Override
                public void onCancel() {

                }

                @Override
                public void onError(FacebookException error) {

                }
            });


     //Facebook için
    private void checkFacebookLoginStatus() {
        if(AccessToken.getCurrentAccessToken()!=null)
        {
            buttonFbLogin.setVisibility(View.VISIBLE);
            buttonLogout.setVisibility(View.GONE);
            loadUserProfile(AccessToken.getCurrentAccessToken());
        }
    }
    // Facebook için   (Giriş-Çıkış için)     //////
    AccessTokenTracker tokenTracker = new AccessTokenTracker() {
        @Override
        protected void onCurrentAccessTokenChanged(AccessToken oldAccessToken, AccessToken currentAccessToken)
        {
            if(currentAccessToken==null)
            {
                // txtName.setText("");
                // txtEmail.setText("");
                ///  circleImageView.setImageResource(0);
                deleteCartTable();
                deleteShoppingCart();
                deleteShPrefencesLogin();
                Intent intent = new Intent(getContext(),MainActivity.class);
                startActivity(intent);
                Toast.makeText(getContext(),"User Logged out",Toast.LENGTH_LONG).show();
            }
            else
                loadUserProfile(currentAccessToken);
        }
    };
    // Facebook için   End   //////

    private void loadUserProfile(AccessToken newAccessToken)
    {
        GraphRequest request = GraphRequest.newMeRequest(newAccessToken, new GraphRequest.GraphJSONObjectCallback() {
            @Override
            public void onCompleted(JSONObject object, GraphResponse response)
            {
                try {
                   String id = object.getString("id");
                    String image_url = "https://graph.facebook.com/"+id+ "/picture?type=normal";


                    RequestOptions requestOptions = new RequestOptions();
                    requestOptions.dontAnimate();



                } catch (JSONException e) {
                    e.printStackTrace();
                }

            }
        });

        Bundle parameters = new Bundle();
        parameters.putString("fields","first_name,last_name,email,id");
        request.setParameters(parameters);
        request.executeAsync();

    }

    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        callbackManager.onActivityResult(requestCode,resultCode,data);
        super.onActivityResult(requestCode, resultCode, data);}
}

fragment_account_profile.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@color/colorBackground"
    android:clickable="true"
    android:focusable="true"
    tools:context=".Controllers.AccountFragment">

   <com.facebook.login.widget.LoginButton
        android:id="@+id/fb_button"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="200dp"
        android:layout_marginEnd="200dp"
        android:layout_marginBottom="382dp"
        android:visibility="visible"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
   app:layout_constraintTop_toBottomOf="@+id/button_acc_Profile_Logout" />


</android.support.constraint.ConstraintLayout>